The filtration of air being circulated by and through heating, ventilating and air conditioning (HVAC) equipment has become an increasingly desirable and necessary process. Historically, air filtration systems and devices associated with HVAC equipment have been provided to maintain the equipment in a state of cleanliness and high efficiency. However, in recent years, the filtration of indoor air has become important to maintain and improve human health and to keep interior rooms and furnishings more clean.
Air filter selection criteria includes filter dirt collection “efficiency”, air pressure drop across the filter, available space for the filter system, dirt or dust holding capacity of the system and, of course, initial and replacement costs. With regard to the filtration of indoor air in residential dwellings and commercial facilities, there has been an increasing need for filters which will perform suitable particle filtration. Conventional electrostatic precipitator type filters are widely used wherein an electrical corona field charges particles approaching the filter structure and particles are collected on high voltage metal plates or electrodes. As dirt accumulates on the filter plates, the efficiency of the filter drops and thus this type of filter generally requires frequent maintenance. In this regard, a type of filter known as an intense field dielectric (IFD) filter has been developed wherein electrodes are sealed within a dielectric material and induce charges on the surface of the dielectric resulting in high efficiency particle collection and wherein the particles give up their charges to maintain the electric field as the air flows through the filter system. U.S. Pat. No. 6,749,669 to Griffiths et al. issued Jun. 15, 2004 is directed to an intense field dielectric type filter system. The subject matter of U.S. Pat. No. 6,749,669 is incorporated herein by reference. The implementation of intense field dielectric filters has, however, posed certain problems in the development of a practical, cost effective filter system that may be incorporated in HVAC equipment, attached as an add-on to HVAC equipment and utilized as a stand-alone filter interposed in an air flow duct, for example. The needs and desiderata associated with implementing the basic configuration of an IFD filter has resulted in the development of the present invention.